A series of deadly bombings across Baghdad that killed at least 63 people and wounded hundreds on Thursday underscored the political and security peril facing Iraq amid rising sectarian tension. Officials said four car bombs and ten other devices were used to target schools, markets and government buildings in at least a dozen neighborhoods over a series of hours. Although no group has yet claimed responsibility, the scale, coordination and civilian targeting prompted analysts to see the signature of al-Qaeda in Iraq in the attacks. And although an operation of this scale would likely have required months of planning, it will have sharply raised the stakes in the escalating sectarian political confrontation between the Shi’ite-dominated government of Prime Minister Nuri al-Maliki and the country’s Sunni political leadership.

Vice President Joe Biden has been on the phone to Baghdad and Erbil this week, frantically trying to coax Iraq’s main political players back from the brink of a new sectarian confrontation less than a week after the last U.S. troops departed. But Iraq’s political leaders paid little heed to Washington’s advice and entreaties when the U.S. had 140,000 troops there; they’re even less likely to comply now. Biden reportedly sought to persuade Maliki to back away from a warrant issued by his government for the arrest of Iraq’s most senior Sunni politician, Vice President Tareq al-Hashimi, on allegations that he was involved in a bomb plot for which members of his security detail have been detained. But Iraq’s Sunni leadership sees the warrant as part of Maliki’s authoritarian crackdown against his opponents, with senior Sunni leaders systematically targeted for arrest by the Shi’ite-led government in recent months.

Al-Hashimi dodged arrest by fleeing to Erbil, capital of the autonomous Kurdish zone in northern Iraq, from where he denounced the arrest warrant as a political plot and accused Maliki of amassing power in his own hands and destroying prospects for inter-sectarian accord. He also offered to stand trial on the allegations, but only in Erbil — the implication being that he didn’t believe he’d get a fair trial in Baghdad. However, there was little sign of Maliki heeding Biden’s call for restraint, or calls by Kurdish leaders for an urgent national conference to discuss the widening sectarian schism in Iraqi politics. The Iraqi Prime Minister declared on TV Wednesday: “I do not allow myself and others to bargain over Iraqi blood.” He demanded that the Kurdish authorities hand over al-Hashimi. “If they will not hand him over or let him flee or escape, this will lead to problems,” Maliki added ominously. While the bombings will have reinforced his narrative about terror threats, it also underscored the danger of allowing a complete breakdown of the political consensus that would, at least in theory, normally function to prevent sectarian violence.

The move against al-Hashimi coincides with the withdrawal from parliament of the predominantly Sunni Iraqiya bloc, prompting Maliki to urge the legislature to pass a vote of no confidence in deputy prime minister Saleh al-Mutlaq, the Sunni faction’s most senior figure in the legislature. And, Maliki warned, the boycott of parliament would result in Iraqiya cabinet ministers losing their positions, ending the inter-party accord that formed the basis of the agreement to seat his government. Iraqiya, whose future participation in what had been envisaged as a consensus government but has in practice been run almost entirely by Maliki’s faction, now appears in doubt, accused Maliki of being “the main cause of the crisis,” and urging his Shi’ite-dominated bloc to put forward an alternative candidate for prime minister.

Many of the Sunni leaders, including al-Hashimi, now support a bid by three Sunni provinces — Anbar, Diyala and Salahuddin — to band together into an autonomous zone on the lines that the Kurds have done. That’s an outcome Maliki is determined to avoid, seeing it as strengthening a beachhead in Iraq of regional forces antagonistic to his rule. Indeed, a union of three provinces that had been the cradle of the Sunni insurgency, and which abut Syria, would strengthen the strategic challenge to Maliki in Baghdad — even more so if President Bashar al-Assad were overthrown by Syria’s Sunni majority. Sunni leaders in those provinces have spoken of Sunni insurgencies on both sides of the Syria-Iraq border amplifying one another. And the al-Qaeda element has always sought to turn Sunnis against participation in the Shi’ite-dominated political system.

The power struggle between Sunni, Shi’ite and Kurdish political factions has been waged in different forms since Saddam’s fall, but it appears to have entered a new phase in recent years, once the clock began ticking down towards the U.S. withdrawal. Maliki has been widely accused of steadily amassing power, particularly through his control over the security forces, and demonstrating his intent to suppress domestic challenges to his increasingly authoritarian rule.

The Prime Minister’s attack on the Sunni political class signals a new round of political brinkmanship, with the danger of a relapse into civil war exacerbated by regional tensions, particularly between Iran — the main outside patron of Maliki’s government — and Saudi Arabia, which has always backed the Sunnis. Those two are at loggerheads in political standoffs throughout the region, from Syria and Lebanon to Bahrain, but Turkey’s growing regional influence has also antagonized Tehran. Ankara has taken a leading role in putting pressure on Iran’s ally in Damascus, President Assad, over his brutal crackdown on a popular rebellion. And last year, Turkey also played a major role in creating and backing the Iraqiya bloc.

There are, of course, a number of domestic factors that might restrain Maliki from pushing the Sunnis over the edge. The Kurdish leadership is again trying to assume a mediating role whose spinoff is to strengthen the autonomy and boundaries of their de facto statelet in northern Iraq. Another key player could be Grand Ayatullah Ali Sistani, the most influential Shi’ite leader in Iraq, who has played a quiet but sometimes decisive role in shaping Iraq’s post-Saddam political transition. Although Sistani comes from the “quietist” tradition that opposes Iran’s system of clerical rule, he has been known to intervene in politics. Sistani forced the U.S. occupation authority to allow Iraqis to elect their own government in January of 2005, and then made sure the various Shi’ite factions didn’t dilute their power by using his influence to corral them into a single political bloc. More recently, Sistani has been strongly critical of corruption and abuse of power in Maliki’s government — so much so that Maliki is reportedly colluding in efforts to install a top Iranian cleric in the Iraqi seminary city of Najaf as a counterweight to Sistani. Sistani remains the single most important leader among Iraqi Shi’ites, and he’s unlikely to countenance a sectarian confrontation with the Sunnis.

The key variable, however, remains Iran. Tehran has been the biggest strategic beneficiary of the U.S. invasion, and it has been the most influential foreign power in Baghdad since the moment the U.S. allowed the Iraqis to choose their own government. (They’ve returned Iran-friendly Shi’ite governments at each election.) While he may be a Shi’ite partisan with an authoritarian streak, but — contra the Saudi view — Maliki is no puppet of Tehran. Still, he’s unable to rule without Tehran’s support; it was Iran’s intervention that persuaded Sadr to throw his considerable parliamentary vote behind Maliki to give him the numbers necessary to keep Iraqiya out of power, after the Sunni-dominated bloc finished with more votes than any other list in the last election.

The question that may determine whether or not Iraq descends into sectarian confrontation, then, may be this: What does Iran want right now?

There may be an argument that stoking instability in Iraq suits Iran at a moment when Tehran is facing growing economic pressure and implied military threats over its nuclear program — a tactic of starting fires in order to demonstrate its ability to cause problems for its adversaries. Yet, there may also be reason to believe that Iran could, in fact, decide to restrain Maliki should his actions appear to be raising the danger of renewed civil warfare. The reason is simple: The status quo put in place in Iraq by the U.S. invasion is a huge strategic gain for Tehran, which saw its most dangerous enemy — Saddam Hussein — replaced by an elected government dominated by its allies. The collapse of that political order in a new round of sectarian bloodshed puts Iran’s post-Saddam gains at risk, also inviting its key regional opponent, Saudi Arabia, to intervene more aggressively to turn Iraq into a proxy battlefield.

Either way, Iran is unlikely to accept matters of such great strategic consequence to the Islamic Republic as a confrontation that could potentially draw in Iraq’s major neighbors can be decided simply by the whims and narrow agenda of Prime Minister Maliki. At a moment when the fate of Iraq’s key Arab partner, Syria’s Assad, hangs in the balance, it would take a stupendous recklessness to roll the dice on its influence in Iraq, also, by encouraging Maliki to overplay his hand.

Indeed, in recent weeks, it has appeared as if Iran has been trying to ease tensions with the Saudis, sending its intelligence minister to Riyadh for talks over the alleged Washington embassy bombing plot, and backing down from opposing the Saudis’ position on OPEC oil output quotas. Saudi foreign minister Prince Saud al-Faisal on Wednesday indicated a willingness to negotiate with Iran to improve recently frayed relations but also warned Iran, via a statement from the Gulf Cooperation Council, against “instigating sectarian strife” in the region.

Unless Iran’s Supreme Leader Ayatullah Ali Khamenei is a more reckless gambler than most analysts know, Prime Minister Maliki may yet find the message he received from Biden discreetly but firmly reiterated by Tehran.

Tony Karon is a senior editor at TIME, where he has covered international conflicts in the Middle East, Asia, and the Balkans since 1997. A native of South Africa, he now resides with his family in Brooklyn, New York.